Heating pen, tack seating device, and tap and surgical implantation methods using same

ABSTRACT

A method, apparatus and system for applying bio-resorbable membranes or plates to bone for internal fixation of bone defects is disclosed.

This application claims the benefit of U.S. Provisional Application No.60/157,825, filed Oct. 5, 1999, the entire contents of which areexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical devices andbio-resorbable plates and membranes and, more particularly, to tools forapplying these plates and membranes to defected bone to splint, containand provide support for the bone to heal.

2. Description of Related Art

A resorbable plate or membrane is typically manufactured with one ormore apertures through which the surgeon can affix the plate or membraneto bone. A widely used technique for fixating a defected bone includesaffixing a bio-resorbable internal fixation device over a defected bonesegment or other bone defect to provide support while the bone defectheals. The internal fixation device, such as a plate or membrane, isaffixed to the damaged bone about the bone defect. The bio-resorbableplate or membrane may be first heated, causing it to become malleable.Once malleable, the bio-resorbable plate or membrane is molded toconform to the contour of the bone area, and subsequently affixed overthat area by, for example, screws to fixate the membrane to the bone.This general technique is set forth, for example, in Lemperle et al,U.S. Pat. No. 5,919,234 entitled RESORBABLE, MACRO-POROUS,NON-COLLAPSING AND FLEXIBLE MEMBRANE BARRIER FOR SKELETAL REPAIR ANDREGENERATION, the entire contents of which are expressly incorporatedherein by reference. During the application process the plate ormembrane hardens as it cools, which may leave, for example, imperfectlyseated portions of the plate or membrane that have been placed prior tothe plate or membrane hardening. In some instances, the surgeon mustthen remove the membrane, heat it, and attempt to position the membraneover the bone defect once again. Moreover, additional time andinconvenience is required for the positioning and securing of the screwsinto the plates or membranes. Neuro-surgeons, for example, wouldgenerally prefer to not be bothered with threading of an aperturedrilled in a bone via the use of a tapping device, with the positioningof a screw properly so that the threads are engaged but not crossed and,subsequently, with the threading of the screw into the threaded apertureto the proper tightness so that the screw is not too loose and yet isnot damaged by over-tightening.

SUMMARY OF THE INVENTION

The present invention provides improved apparatus, systems, and methodsfor shaping and attaching bio-resorbable plates and membranes to bonedefect areas. In accordance with one aspect of the present invention, aresorbable plate or membrane is submerged in a hot solution until itbecomes malleable. Once malleable, the plate or membrane is molded toconform to the contours of the bone defect area, and subsequently fixedover that area. During the application process the plate or membranehardens as it cools, which may leave, for example, imperfectly seatedportions of the plate that have been placed prior to plate or membranehardening. In accordance with one aspect therefore, the improvedapparatus, systems and methods of the present invention advantageouslyallow the surgeon to further closely shape the plate or membrane to thecontours of the bone, in vivo, once the plate or membrane cools andhardens after the initial shaping.

The in vivo molding or shaping of plates and membranes is accomplishedwith the use of a heating pen. The heating pen comprises a handle and ashaper. At the distal end of the handle is a nose, which includes twoconductive apertures. The shaper comprises a pair of parallel conductiveprongs that fit into the conductive apertures at the nose of the handle.The prongs are held together by a disk shaped housing. Opposite theprongs is an extender. At the tip of the extender is a heating metalpad, which is engineered to rapidly transfer heat to the material of themembrane or plate to thereby bring the material to its glass transitiontemperature, where the membrane or plate becomes malleable.

In use, the plate or membrane is first submerged in a heated solutionuntil it reaches its glass transition temperature and becomes malleable.The plate or membrane is then placed over a bone defect, where it beginsto harden as it cools. To maintain the malleability of the plate ormembrane, the surgeon holds the heating pen and heats up the heatingpad, which is preferably metal, by compressing an outwardly biasedlever. Once the metal pad is heated, the surgeon directs the metal padagainst the hardened plate or membrane in vivo to warm the plate ormembrane, causing it to once again become malleable. In this manner thesurgeon can further form the malleable plate or membrane onto the bonefor a better fit, for example, by maneuvering and compressing the heatedmetal pad about the plate or membrane.

Additionally, the improved apparatus, systems and methods of the presentinvention allow the surgeon to fix the plate or membrane to the bonequickly and efficiently using tacks. One aspect of the present inventionentails the use of a tack fastener and a tack seating device toconveniently and effectively place tacks through an internal fixationdevice and into the bone. In accordance with one aspect of the presentinvention, a tack seating device is provided for automatically seatingthe tacks into a bone hole prepared by the surgeon. Each tack isautomatically seated with a driving force produced by the tack seatingdevice to allow secure seating of the tack wherein the manual drivingforce for insertion of the tack is limited to a period of time on theorder of about one second.

The fasteners used in accordance with one feature of the presentinvention are bio-resorbable tack fasteners. Bone screws are a secondtype of fastener. Each tack fastener comprises a head, a shaft andradial protrusions along the length of the shaft. The tack seatingdevice is equipped with an end to receive the head of a tack. The tackis then automatically seated via a driving force by the tack seatingdevice.

A cutting filament for cutting plates, tacks, screws, and otherresorbable or plastic elements, may also be used with the heating pen.The heating pen allows the surgeon to cut away surplus portions of theplate, membrane, or other implants. Once the cutting filament is heated,the surgeon directs the filament against the plate, membrane, or otherimplant, in vivo, to cut the plate, membrane or implant. In this mannerthe surgeon can further form the plate, membrane, or other implant ontothe bone for a better fit, for example, by removing surplus edges ormaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of the tack seating device of the presentinvention in the relaxed position.

FIG. 1B is a side view of the tack seating device of the presentinvention in the “cocking” position.

FIG. 1C is a side view of the trigger mechanism of the tack seatingdevice of the present invention.

FIG. 2 is a side cross-sectional view of a tack fastener engaged withthe tack seating device of the present invention, in the “cocked”position.

FIG. 3 is a side view of the trigger mechanism of the tack seatingdevice of the present invention.

FIG. 4 is a side view of the embodiment of the present invention of amanual tack seating device of the present invention.

FIGS. 5A and 5B are side cross-sectional views of the grooved section ofa manual embodiment of the tack seating device of the present invention.

FIG. 6A is a side view of the trigger mechanism of the tack seatingdevice of the present invention, in the relaxed position.

FIG. 6B is a side view of the trigger mechanism of the tack seatingdevice of the present invention, in the “cocked” position.

FIGS. 7A–7E are side cross-sectional views of a tack fastener being usedin conjunction with the tack seating device of the present invention.

FIG. 8A is a perspective view of the tack-fastener container of thepresent invention; FIG. 8B is a detailed cross-sectional view of thetack-fastener container and tack seating device in use.

FIG. 9 is a side view of the tack fastener of the present invention.

FIG. 10 is a detailed side view of the tack fastener being engaged bythe tack seating device of the present invention.

FIG. 11 is a schematic side view of a tack fastener of the presentinvention.

FIG. 12A is a schematic side view of a tack of the present inventionprior to insertion into a bone hole.

FIG. 12B is a schematic side view of the tack of FIG. 12A after beingdistorted by insertion into a bone hole.

FIG. 13 is a side view of the heating pen device of the presentinvention.

FIG. 14 is a side exploded view of the heating pen device of the presentinvention.

FIG. 15 is a side view of the heating pad portion with an extender forthe heating pen device of the present invention.

FIG. 16 is a side view of a cutting filament for the heating pen deviceof the present invention.

FIG. 17 is a side view of the cap for the heating pen device of thepresent invention.

FIGS. 18A–C are side views of fluted screw taps in accordance with thethe present invention.

FIG. 18D is a top view of the fluted screw tap of FIG. 18-C.

The present invention, together with additional features and advantagesthereof, may best be understood by reference to the followingdescription taken in connection with the accompanying illustrativedrawings.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring more particularly to the drawings, FIGS. 1A–1C illustrate atack seating device 31 for automatically seating a tack fastener into abone aperture. The tack seating device 31 is constructed to apply asingle, predetermined driving force to the tack fastener to therebyquickly and consistently seat the tack fastener into a bone aperture.Thus, manual driving forces and periods of time greater than about asecond are not required of the surgeon for seating each tack fastener.

The tack seating device 31 thus provides for a reliable and brisk entryof the tack fastener into the bone aperture, whereas manual seatingdevices may require iterative pressures or rotations, for example, toset each radial protrusion of the tack fastener into a bone aperture.The iterative pressing in such manual seating operations may createexcessive pressure at the damaged bone area and cause collapse orundesired movements of the bone fragments. Moreover, the iterativepressing may damage the tack fastener. Tapping of bone apertures toreceive screws can present similar problems.

In accordance with the present invention, the tack seating device isconstructed and calibrated to provide a relatively precise drivingpressure required for seating the tack fastener each time. The surgeonpositions the tack fastener for seating and then activates the drivingmechanism of the tack seating device. The tack seating device 31preferably comprises a cylindrical housing 33 which includes a tackholder 35, a plunger 37 (FIGS. 6 and 7), a plunger spring 39 for drivingthe plunger 37, a tack-holder spring 51 for retracting the tack holder,and a trigger or release mechanism 41 for releasing the plunger spring.The tack holder distal end comprises a hollow cylindrical structure withan opening or mouth 43 at the tip. FIGS. 1A, 6A and 7A show the tackseating device in the relaxed position with the plunger 37 fullyextended within the tack holder 35. As shown in FIGS. 1B, 7A, 7B and 7C,when pressure is applied to the tack holder distal end, both the tackholder 35 and the plunger 37 move and compress the plunger spring 39 andthe tack-holder spring 51. The plunger 37 is thus moved proximally in adirection of the arrow A1 within the cylindrical housing 33, to a cockedposition in which the lever 47 travels in a direction of the arrow A2,as shown in FIGS. 1B and 6B. The plunger 37 is retained in the cockedposition by the pin 45 of the trigger or release mechanism 41, as shownin FIGS. 1C and 6B, but the tack holder 35 returns distally in adirection of the arrow A3 to its FIG. 1A position. The tack drivingplunger 37 is released by the trigger or release mechanism 41 bydepressing the lever 47, as shown by the arrow A4 in FIG. 1C.

The opening or mouth 43 at the end of tack holder 35 is detailed in theembodiment illustrated in FIGS. 2 and 3. The mouth is formed with aninternal radial groove 49 sized to be of slightly smaller diameter thanthe head of a given tack fastener. For example, as shown in FIGS. 2 and3, the opening 43 can be optimally sized at about 3.98 mm for use with atack fastener 50 having a tack-fastener head 50 a diameter of about 4mm, but other tolerances are possible. The diameter of the opening 43 istherefore slightly smaller than the diameter of a tack-fastener head. Assuch, the tack-holder opening stretches/deforms and/or the tack-fastenerhead compresses sufficiently to allow the enlarged-diameter portion ofthe tack-fastener head to slide into the interior of the tack holder 35.In the illustrated embodiment the radial groove 49 is of about 0.02 mmin depth, as is also shown in FIGS. 5A and 5B. Other groove depths orother tack holding structures may be incorporated so long as the tackfastener can be gripped and firmly held without substantial deformationof the tack fastener. The plunger 37 is preferably centrally coaxial tothe tack holder 35, The tack holder 35 in this embodiment is actuated bythe tack-holder spring 51, and the plunger 37 is actuated by the plungerspring 39. The radial groove 49 is preferably disposed near to theopening, so that shortly after the tack-fastener head penetrates theopening, it snaps into the radial groove 49, providing for a firmholding of the tack-fastener head, and thus the tack fastener 50.

In accordance with a modified embodiment of the present invention, atack fastener may be seated within a manual tack seating device 52, asshown in FIG. 4. The manual tack seating device 52 is a simple mandrelthat operates similarly to the tack fastener in loading and seating thetack fastener, but requires manual driving of the tack fastener into thebone aperture. As shown in FIGS. 5A and 5B the manual tack seatingdevice embodiment similarly has a tack-holder end 35′ with an opening ormouth 43′ having a radial groove 49′ to retain the end of a tackfastener. FIG. 5B shows a cross-sectional side view of the holder end35′.

Referring now to FIGS. 6A and 6B the operation of the preferredembodiment of the trigger or release mechanism 41 of the tack seatingdevice 31 of the present invention is illustrated. The plunger 37 iscoaxially situated in the center of the hollow tack holder 35. Theplunger 37 is coupled to plunger spring 39 and the tack holder 35 iscoupled to a tack-holder spring 51. In the relaxed position, the springs39 and 51 are uncompressed, and the distal ends of the plunger 37 andtack holder 35 protrude from the cylindrical housing 33. When axialexternal pressure is placed on the tip of the plunger 37 and the tackholder 35, the plunger 37 and tack holder 35 retract into thecylindrical housing 33 causing the respective springs 39 and 51 to whichthey are coupled to compress in the direction shown by arrow A1. Thecompressed plunger spring 39 that is coupled to the plunger 37 iseventually held in the compressed position while the tack-holder spring51 that is coupled to the tack holder 35 is allowed to be moved into itsdecompressed position. Consequently, the compressed spring 39 to whichthe plunger is coupled, when decompressing, provides the driving forcefor the plunger 37 to move distally and drive the tack fastener into thebone aperture, with the proper amount of force for proper seating of thetack fastener.

Referring now to FIGS. 7A–7E and 8A–8B, in a preferred embodiment theaxial pressures to compress the springs 39 and 51 are provided by theloading of the tack type of fastener 50. To load the tack fastener, thetack holder mouth 43 is axially pressed against the tack-fastener headas shown in 7A while the tack fastener is stored in a tack-fastenercontainer 53 shown in FIG. 8A. The tack-fastener container serves as astable support to position the tack fastener for it to be picked up bythe tack seating device, by an assistant for example. The tapering fromthe top of the tack-fastener head allows the tack holder of the tackseating device to slide over the tack-fastener head with relative ease.The tapering from the lower surface allows for an adequate scaled spacefor the tack holder to completely envelop the tack-fastener head,wherein the tack-fastener head snaps into the radial groove, for amechanical and audible positive feedback of proper operation. The axialcompression of the tack holder against the tack-fastener head allows forthe tack-fastener head to be picked up and also for the plunger to becocked. Once cocked, the plunger can be released by the surgeon pressingon the other end of the lever to release the pin, to thus release thespring from compression. The released spring causes the plunger to moveforward and drive the plunger axially against the tack-fastener head.The tapering on the lower surface of the tack-fastener head allows thetack-fastener head to smoothly slide out of the groove and into the boneaperture as the plunger presses against the tack-fastener head.

Once seated within the radial groove 49 of the tack holder, thetack-fastener head 50′, detailed in FIGS. 7E and 8B, upon continuedloading forces exerted by the surgeon, as shown in FIGS. 7A–7C, exertspressure against an interior surface 55 (FIG. 8B) of the tack holder 35.The proximally directed pressure of the tack-fastener head 50′ againstthe interior surface 55 forces the tack holder 35 to retract into thecylindrical housing against the bias of the tack-holder spring 51. Asthe tack-fastener head 50′ presses against the interior flat surface 55of the tack holder 35, it also comes into contact with the distal tip 85of the plunger 37 and exerts proximal pressure against the plunger 37causing the plunger 37 to retract against the bias of the plunger spring39, as shown in FIGS. 7A–7C. This all preferably occurs in one fluidmotion as the surgeon loads the tack fastener 50 from the tack-fastenercontainer 53. In accordance with the presently preferred embodiment,both the tack holder 35 and the plunger 37 are separately spring loaded,and are both eventually loaded into a compressed position within thetack holder, as shown in FIG. 7C. The tack holder 35 is subsequentlyallowed to be moved into its decompressed position, as shown in FIGS. 6Band 7D.

Referring again to FIGS. 6A and 6B, the compressed plunger spring 39 andplunger 37 remain in a compressed (cocked) position by the trigger orrelease mechanism 41, while the tack holder 35 returns to the relaxedposition. The shaft of the plunger 37 is one cylindrical unit havingsmaller 37 a and larger 37 b diameter segment, with the smaller diametersegment 37 a protruding from the cylindrical housing 33. As such, thereis effectively a step 37 c from the larger diameter segment 37 b to thesmaller diameter segment 37 a of the plunger shaft. The lever 41 restson the exterior surface of the cylindrical housing 33 and extendsaxially along a portion of the length of the cylindrical housing 33. Ata proximal end of the lever 41 is a pin 45, which extends into thecylindrical housing 33. In the relaxed position of FIG. 6A, the pin 45exerts an inward force onto the larger diameter segment 37 b under theinfluence of a lever spring 57 which is disposed between a distal end ofthe lever 41 and the exterior surface of the cylindrical housing 33. Asshown in FIG. 6B, when the plunger 37 retracts proximally, the smallerdiameter segment 37 a of the plunger 37 moves toward the pin 45 in thedirection of the arrow A1. Eventually, the pin 45 moves down the step 37c from the surface of the larger diameter segment 37 b to the surface ofthe smaller diameter segment 37 a of the plunger. As the lever spring 57expands, the pin 45 drops to the smaller diameter segment 37 a. Theproximal side of the pin 45 will rests against the step 37 c when thecompressed plunger spring 39 is locked into the cocked position.

The trigger mechanism is released by removing the pin 45 from the step37 c by pressing the lever 71. When the pin 45 is removed from the step37 c, the plunger spring 39 decompresses and drives the plungerdistally, hammering the tack fastener 50 out of the tack holder 35 andinto the bone aperture. The tack seating device 31 of the presentinvention can thus almost instantaneously secured the tack fastener 50into the pre-drilled bone aperture. As a result, a market advantage andreduction of the possibility of human error are present with the systemand apparatus of the present invention. The neuro-surgeon, for example,can quickly drill an aperture that will subsequently receive a tackfastener which has been pre-seated within the tack seating device 31 byan assistant. The neuro-surgeon can thus orient the tack seating device31 for seating the tack fastener 50, and press the trigger 41 tocompletely seat the tack fastener 50, allowing the surgeon toconcentrate more of his or her on other surgical tasks.

The fasteners used in accordance with one feature of the presentinvention are bio-resorbable tack fasteners. Referring now to FIG. 9each tack fastener 50 comprises a head 50 a, a shaft 50 b and radialprotrusions 50 c along the length of the shaft. The tack fastener usedin one illustrated embodiment has a head diameter of 4.0 mm (shown atq), a shaft length of 4 to 6 mm (shown at r), a shaft minor diameter of1.4 mm (shown at s), and a shaft major diameter of 1.7 mm (shown at t),for a bone aperture of 1.5 mm in diameter (shown at u). The radialprotrusions 50 c are spaced from point to point at a distance of about0.6 mm (shown at v). The illustrated tack fastener has four radialprotrusions which are preferably annular. The radial protrusions aredesigned to deformed 5 to 15 percent in the illustrated embodiment, toallow for the tack fastener to snugly fit in the pre-drilled boneaperture 59, which has a diameter of 1.5 mm. In modified embodiments,other scales, configurations, numbers of protrusions, and deformationpercentages may be used.

In a preferred embodiment of the invention, shown in FIG. 10, the head50 a of the tack fastener 50 is tapered off at an angle from the topsurface x and tapered from the lower surface y, providing for the outerperipheral edge of the head to be thinner than its center portionsthereof, measured in a direction parallel to the tack axis. The radialprotrusions 50 c on the shaft 50 b in the illustrated embodiment aresymmetrically angled from the top surface and the lower surface. Inaccordance with other embodiments of the present invention, theperipheral edge of the head 50 a may be rounded, providing for the outerperipheral of the head to be thinner than center portions; the radialprotrusion may be angled from the lower surface only to form barbs; orthere may be more or fewer radial protrusions on the shaft.

Another illustrated dimensional configuration is shown in FIG. 11,wherein the tack fastener comprises a shaft 50 b with a length of about2.5 mm, shown at y, and a pointed tack-fastener tip 50 d. The radialprotrusions 50 c of this exemplary tack fastener have a major diameterof about 0.9 mm, shown at v, and a shaft minor diameter of about 0.8 mm,shown at w. The major diameters of the radial protrusions are spacedabout 0.5 mm apart, shown at u, and the tack-fastener head 50 a, shownat x, has a diameter of about 2.25 mm.

FIGS. 12A and 12B show the distorting effect that insertion into a boneaperture has on the radial protrusions of an exemplary tack fastener 50.In particular, FIG. 12A shows the dimensions of a bone screw prior toinsertion, and FIG. 12B shows the effect on the tack fastener aftercompression into a bone aperture. The tack fastener has a shaft 50 bminor diameter of about 1.2 mm both before and after compression, shownat u′ and u. The distance between the radial protrusions is also thesame before and after compression, about 0.5 mm, shown at w′ and w. Theradial protrusions 50 c, however, have been inelastically distortedafter tack-fastener insertion into a bone aperture, as shown in FIG.12B. The major diameter of the radial protrusions have been reduced fromabout 1.5 mm, shown as v′ in FIG. 12A, to only about 1.35 mm, shown at vin FIG. 12B, for an overall loss of major diameter of about ninepercent. The contact area between the tack fastener and the wall of thebone aperture is thus increased, due to the flattening of the radialprotrusion, as shown at z′ and z, strengthening the tack fastener'spurchase on the bone aperture.

In accordance with another aspect of the present invention, a heatingpen apparatus is used for in vivo molding of plates and membranes.Referring to FIGS. 13–17, the heating pen 61 in the illustratedembodiment comprises a handle 63 and a shaper 65. The handle 63 ispreferably tubular, with an interior battery compartment 67. On theproximal end of the handle is an insertion slot for batteries 69. On thesurface and close to the distal end of the handle is a lever 71, biasedoutwardly. At the distal end of the handle is a nose 73. The nose hastwo conductive apertures 75. The shaper 65 comprises a pair of parallelconductive prongs 77 that fit into the conductive apertures 79 at thenose 73 of the handle. The prongs are held together by a disk shapedhousing 81. Opposite the prongs is an extender 83, and at the tip of theextender is a heating pad 87, which as presently embodied comprisesmetal. The heating pad is engineered to rapidly transfer heat to thematerial of the membrane or plate to thereby bring the material to itsglass transition temperature. Once brought to its glass transitiontemperature, the membrane or plate will become malleable.

In accordance with a method of the present invention, the plate ormembrane is first heated to its glass transition temperature bysubmersion into a heated solution, and then placed ono bone. The heatedsolution preferably comprises a saline solution, but alternatively maycomprise any biocompatable fluid suitable for heating resorbableplastics. After the plate or membrane has been placed and shaped, itwill begin to cool and harden, The surgeon can then activate the heatingpen 61 to heat the heating pad by compressing on the outwardly biasedlever 71. Once the metal pad is heated, the surgeon directs the metalpad against the hardened plate or membrane in vivo, to further heat andform the plate or membrane onto the bone. The heated metal pad willcause the hardened area of the plate or membrane to become malleable.Once malleable, the surgeon can shape the plate or membrane, forexample, by maneuvering and compressing the heated metal pad about theplate or membrane. The shaper 65 may alternatively be formed with alonger extender 83′ to allow easier access to a plate or membrane by thesurgeon, as shown in FIG. 15. The electricity for the heating pen mayalternatively be supplied by standard 120 volt/60 Hz AC utility wallsocket after being appropriately transformed to a safely loweredvoltage.

There is shown in FIG. 16 a cutting filament 91 for cutting plates thatmay also be used with the heating pen in place of the shaper 65, alsohaving parallel conductive prongs that fit into the conductive aperturesof the heating pen in the same manner as the shaper. With thisattachment the heating pen 61 allows the surgeon to cut away surplusportions of the plate, membrane, tack, screw or other elements. Once thecutting filament is heated, the surgeon directs the filament against thehardened plate or membrane in vivo to cut the plate, membrane, fasteneror other plastic element. In this manner the surgeon can further formthe plate or membrane onto the bone for a better fit, for example, byremoving surplus edges. Additionally, the head or heads of tack orscrews may be cut off for removal of a plate or membrane. The cuttingfilament may also be used, for example, to remove the portion of amisplaced tack fastener protruding from a misplaced bone aperture. A cap93 is provided for the heating pen 61 that is large enough to allowstorage with the shaper or filament attachment attached. The capcomprises slot 93′ to allow the cap to pass about the outwardly biasedlever when seated.

In practice, the bio-resorbable plate or membrane, the heating pen, tackfastener, tack-fastener container, and the tack-fastener seating devicework together as a system. Generally, the plate or membrane is submergedinto a hot solution (saline water, for example) to become malleable.Once malleable, the plate or membrane is shaped to the contour of thebone area to be covered. The shaped plate or membrane can then in oneembodiment be tacked to the bone surface. The molding of the plate ormembrane and the insertion of tacks or screws may be an iterativeprocedure. For example, the surgeon inserts one tack fastener through amembrane with the tack seating device 31, molds the membrane in vivowith the shaper 65 of the heating pen 61, inserts another tack fastenerwith the tack seating device 31, performs additional molding with theshaper 65, inserts another two or more tack fasteners with the tackseating device 31, further molds the membrane with the shaper 65,inserts additional tack fasteners with the tack seating device, andremoves unwanted portions of the membrane with the heating filament 91of heating pen 61. The tack fasteners to be used are held and removed,for example, in the tack-fastener container 53 of the type and in theway as set forth above.

In certain instances, the surgeon may want to use an alternativefastener, for example, a screw. In this particular instance, theapertures in the bone will need to be tapped. The new apparatus fortapping the bone apertures provides for optimal threading of theaperture. A traditional problem of tapping is that too much bone debrismay be left in the bone aperture. The bone debris can clog the apertureand/or effectively strip the thread inside the aperture. The presentinvention addresses this problem.

Referring now to FIGS. 18A–18D, in a preferred embodiment, the tap 95has two short flutes 95 a and two long flutes 95 b. The relativelyextensive fluting of the tap of the present invention allows foradditional void volume between the bone and the tap. This additionalvoid volume can better collect the bone debris, and thus efficientlyremove them from the aperture. Although four long flutes would providemore space for bone debris to be collected, it has been discovered thatthe alternating short and long flutes of the present invention providebetter performance with sufficient void volume and adequate structuralstrength/integrity of the shaft 95′ of the tap.

As a modification to the method set forth above, resorbable screws maybe used in addition to or as an alternative to the tack fasteners. Themethod would otherwise be similar, except for the fact that drilledapertures must be tapped. The tapping device of FIGS. 18A–D may be used,or a conventional tap used, in accordance with the present invention. Abio-resorbable plate or membrane is placed in hot water to bring it toglass transition temperature, making the plate or membrane malleable andpliable. The plate or membrane is placed over the bone defect area andshaped appropriately. The bone apertures where the tack fasteners and/orscrews are to be inserted can be drilled and/or tapped, either before orafter the plate or membrane is placed over the bone area, oriteratively. For example, an aperture is drilled and tapped, one screwis placed through a membrane, the plate or membrane is molded with theheat pen, another tack fastener or screw is placed, additional moldingwith the heat pen occurs, etc. The heated water bath, heating pen, tackseating device, and tap, can thus be used throughout the implantationprocess.

The aforesaid detailed description, and the figures to which it refers,are provided for the purpose of describing examples and specificembodiments of the invention only and are not intended to exhaustivelydescribe all possible examples and embodiments of the invention. Manyother changes, modifications and substitutions, in addition to those setforth in the above paragraphs, may be made by one having ordinary skillin the art without necessarily departing from the spirit and scope ofthe present invention.

1. A method for affixing a bone plate or membrane to a bone comprising:a) drilling an aperture in a bone; b) placing a bone plate or membranein hot solution to bring it to glass transition temperature; c) locatingor creating a hole in the bone plate or membrane; d) aligning theaperture in the bone plate or membrane with the aperture in the bone; e)loading a tack seating device with a tack fastener, wherein the tackseating device comprises a member having a handle end and a tack holderdistal end that includes a portion with an internal radial groove sizedto receive the head of the tack fastener and loading is achieved byseating the head of a tack fastener within the internal groove toocclude the tack holder; and f) inserting the tack fastener through theaperture in the bone plate or membrane and the aperture in the bone withthe tack seating device.
 2. The method for affixing a bone plate ormembrane to a bone of claim 1, wherein the tack seating device includes:a) a handle having a tack holder distal end; b) a plunger actuated by aplunger spring—within the handle, the plunger being movable from arelaxed position to a cocked position wherein the plunger spring iscompressed; and c) a retaining mechanism to retain the plunger in thecocked position and further to release the plunger and cause the plungerto contact the tack fastener and move it into the bone aperture.
 3. Themethod for affixing a bone plate or membrane to a bone of claim 2, andfurther including: a) providing a heating pen, the heating pen includinga switch which is in electrical communication with an electric powersource, and further including a heating pad which is in electricalcommunication with the switch; b) heating the heating pad by passingelectrical current from the switch to the heating pad; c) placing theheating pad in contact with a portion of the bone plate or membrane tothereby bring the bone plate or membrane to its glass transitiontemperature; d) bending or shaping the heated bone plate or membraneportion to conform to the contour of the bone.
 4. The method foraffixing a bone plate or membrane to a bone of claim 2, and furtherincluding: a) providing a heating pen having a handle with a switch forproviding electrical power to a filament—affixed to the handle; c)heating with the filament a portion of the bone plate or membrane to itsglass transition temperature; d) cutting a portion of the plate ormembrane with the filament of the cutting filament.
 5. A methodfor—shaping or forming a bone plate or membrane in vivo, comprising: a)applying a bone plate or membrane that becomes malleable at a glasstransition temperature to a bone; b) providing a heating pen having ahandle with a switch for providing electrical power to a heating pad,which is affixed via an extender to a distal end of the handle and whichcomprises a contacting surface with an enlarged width, measured in adirection transverse to a longitudinal axis of the extender, relative toa corresponding reduced width of the extender, that is constructed tocontact and apply heat to a bone plate or membrane; c) heating with theheating pad a portion of the bone plate or membrane to its glasstransition temperature, while the bone plate or membrane is within apatient; and d) bending or shaping the heated bone plate or membraneportion to conform to the contour of the bone.
 6. The method for shapingor forming a bone plate or membrane in vivo of claim 5, and furtherincluding: a) providing a heating pen having a handle with a switch forproviding electrical power to a filament affixed to the handle; c)heating with the filament a portion of the bone plate or membrane to itsglass transition temperature; and d) cutting a portion of the plate ormembrane or of the tack fastener applied to the bone with the filament.7. The method of claim 5, wherein the providing comprises providing aheating pad with a contacting surface having a cross-sectional area thatis greater than a cross-sectional area of the extender.
 8. The method ofclaim 5, wherein the providing comprises providing a heating pad with acontacting surface having a cross-sectional area that is greater than across-sectional area of the extender at a point where the heating pad isaffixed.
 9. The method of claim 5, wherein the providing comprisesproviding a heating pad with a contacting surface having across-sectional area that is greater than a cross-sectional area of theextender, the cross-sectional areas being measured in a directiontransverse to a longitudinal axis of the heating pen.
 10. The method ofclaim 5, wherein: the handle comprises a proximal portion, a distalportion to which the heating pad is affixed, and an axis extendingbetween the proximal portion and the distal portion; and the providingcomprises providing a heating pad with a cross-sectional area that isgreater than a cross-sectional area of the extender, the cross-sectionalareas being measured in a direction transverse to the axis.
 11. A systemfor applying a bone plate or membrane to a bone, comprising: a) a tackseating device including a handle member having a handle end and a tackholder distal end, the tack holder distal end having a portion with aninternal radial groove sized to receive the head of a tack fastener andfurther including a trigger or retaining mechanism to retain a plungerin a cocked position and further to release the plunger and cause it tocontact the tack fastener and move it distally out of the internalradial groove and into the bone; b) a heating pen for shaping or forminga bone plate or membrane in vivo, including a handle member having anose end with conductive members and a switch to control the flow ofelectricity to the conductive members; c) a shaper affixable to theheating pen and having conductive elements and a heating pad inelectrical communication with the conductive elements, wherein whenaffixed to the nose end of the heating pen the shaper can be heated byway of the conductive members and conductive elements sufficiently toenable the shaper to bring a bone plate or membrane to its glasstransition temperature; and d) a cutting filament affixable to theheating pen and having conductors, wherein when affixed to the nose endof the heating pen the cutting filament can be heated by way of theconductive members and conductors sufficiently to enable the cuttingfilament to cut through a resorbable bone plate or membrane.
 12. Abeating pen for shaping or forming a bone plate or membrane in vivo,comprising: a) a handle member having a nose end with conductive membersand a switch to control the flow of electricity to the conductivemembers; and b) a shaper having a heating pad and an extender affixableto the nose end of the handle member so that conductive elements are inelectrical communication with the conductive members, a distal tip ofthe heating pad having a first cross-sectional area that is greater thana second cross-sectional area of the extender and the heating pad beingcapable of heating to and remaining at a temperature suitable to bring aresorbable bone plate or membrane to its glass transition temperature.13. The heating pen for shaping or forming a bone plate or membrane invivo of claim 12, further comprising—a cutting filament having afilament affixable to the nose end of the handle member so that theconductive elements are in electrical communication with the conductivemembers, wherein the filament will beat to a temperature sufficient tocut through a resorbable bone plate or membrane.
 14. The heating pen forshaping or forming a bone plate or membrane in vivo of claim 12, whereinthe heating pad comprises a non-convex contacting surface constructed tocontact and apply heat to a bone plate or membrane.
 15. The heating penfor shaping or forming a bone plate or membrane in vivo of claim 14, thecross-sectional areas being measured in a direction transverse to alongitudinal axis of the heating pen.
 16. The beating pen for shaping orforming a bone plate or membrane in vivo of claim 12, wherein theheating pad has a contacting surface with a cross-sectional area that isgreater than a cross-sectional area of the extender.
 17. A tack fastenerdevice for affixing a bone or plate to bone, comprising a member havinga handle end and a tack holder distal end that includes a portion withan internal radial groove sized to receive and hold a head of the tackfastener and further comprising a plunger that can be actuated tocontact a proximal part of the tack fastener and drive it distally outof the internal radial groove and into the bone wherein: the plunger canbe actuated by a plunger spring that can be moved from a relaxedposition to a cocked position wherein the plunger compresses the plungerspring; and the tack fastener device further comprises a trigger orretaining mechanism to retain the plunger in the cocked position andfurther to release the plunger and cause it to contact the tack fastenerand move it outwardly.
 18. The tack fastener of claim 17, wherein thetack holder distal end is biased by a tack holder spring and isconstructed to move coaxially with the plunger from an unbiased positionto a biased position.
 19. The tack fastener of claim 18, wherein thetack holder distal end moves to the biased position while the plunger isbeing moved from a relaxed position to a cocked position, and thenreturns to an unbiased position while leaving the plunger in the cockedposition.
 20. A tack fastener device for affixing a bone or plate tobone, comprising: a plunger actuated by a plunger spring that can bemoved from a relaxed position to a cocked position wherein the plungercompresses the plunger spring; a member having a handle end and a tackholder distal end that includes a portion with an internal radial groovesized to receive and hold a head of the tack fastener, the tack holderdistal end being biased by a tack holder spring and being constructed tomove coaxially with the plunger from an unbiased position to a biasedposition; and a trigger or retaining mechanism to retain the plunger inthe cocked position and further to release the plunger and cause it tocontact the tack fastener and move it outwardly.
 21. The tack fastenerof claim 20, wherein the tack holder distal end moves to the biasedposition while the plunger is being moved from a relaxed position to acocked position, and then returns to an unbiased position while leavingthe plunger in the cocked position.
 22. A method for shaping or forminga bone plate or membrane in vivo, comprising: a) applying a bone plateor membrane that becomes malleable at a glass transition temperature toa bone; b) providing a heating pen having a handle with a switch forproviding electrical power via an extender to a heating pad, wherein theextender is affixed to an affixation part at a distal end of the handleand the heating pad has a first cross-sectional area that is greaterthan a second cross-sectional area of the extender; c) heating with theheating pad a portion of the bone plate or membrane to its glasstransition temperature, while the bone plate or membrane is within apatient; and d) bending or shaping the heated bone plate or membraneportion to conform to the contour of the bone.
 23. The method of claim22, wherein the providing comprises providing a heating pad with acontacting surface having a cross-sectional area that is greater thanthe second cross-sectional area.
 24. The method of claim 22, wherein theproviding comprises providing a heating pad with the firstcross-sectional area being greater than the second cross-sectional area,the cross-sectional areas being measured in a direction transverse to alongitudinal axis of the heating pen.
 25. The method of claim 24,wherein: the providing comprises providing a handle having a proximalportion and a distal portion that includes the affixation part; and thelongitudinal axis extends between the proximal portion and the distalportion.